1. Technical Field
The present invention relates to a hologram reproduction method and apparatus, and particularly relates to a hologram reproduction method and apparatus that can record a Fourier transformed hologram in a state with a 0-order component removed from a signal light, restore and reproduce the original signal light from the recorded hologram, and reproduce recorded digital data accurately.
2. Related Art
In holographic data storage, digital data “0”, “1” is digitally imaged (formed into signal light) as a contrast of “light” and “shade”, and the signal light is Fourier-transformed by a lens and irradiated onto an optical recording medium. Accordingly, a Fourier-transformed image is recorded on the optical recording medium as a hologram. The Fourier-transformed image in digital data has quite strong peak intensity in the 0-order component. In the holographic data storage, therefore, a dynamic range of the optical recording medium is consumed by the 0-order component (DC component), and if it is tried to increase the degree of multiplexing (the number of holograms to be multirecorded), an S/N (signal to noise) ratio of the reproduced image is considerably deteriorated, thereby causing a problem in that the degree of multiplexing cannot be increased.
In order to address the above, various methods for intercepting the DC (0-order) component in the Fourier-transformed image of the signal light have been proposed.
However, if the 0-order component is removed from the Fourier-transformed image of the signal light, an intensity pattern different from an original data image appears on a reproduced image, and hence, digital data cannot be decoded accurately. That is, if the 0-order component is removed from the Fourier-transformed image of the signal light to perform record reproduction of the hologram, the intensity pattern of the reproduced image becomes a pattern different from the intensity pattern generated by a spatial light modulator at the time of recording. For example, in the above method, only the image edge portion is reproduced, and hence, the digital data may not be decoded accurately.